Yes, but the expiry rules are different for each credit type.
Free Credit
Free Credit resets at the end of every billing cycle. Unused Free Credit does not carry over to the next month.
Main Credit
From your subscription: expires at the end of your current billing cycle. Does not roll over.
From a top-up: expires 1 year from the date of purchase.
From promotions: expiry follows the terms of the specific promotion.
Credits are consumed in order of earliest expiry first, so the credits closest to expiring are always used first.
Note: You'll receive an email notification when any Main Credits are expiring within 7 days.